The field of the invention relates to the culturing of microorganism samples, and more particularly to a three-piece all-in-one device that stores, rehydrates, and extracts, transfers, and streaks a microorganism sample in a sterile environment without the need for additional implements such as transfer pipettes or inoculation loops, with the goal of achieving isolated colonies of cultured microorganism growth in a nutrient-rich environment.
Laboratory professionals use known freeze-dried microorganisms to validate test procedures and laboratory results. These known microorganisms, for example Escherichia coli, have distinct growth characteristics and reactions to biochemicals. Such microorganisms are commercially available to laboratories that perform microbiology testing. Diagnostic testing systems rely on the distinct growth characteristics and reactions of such microorganisms.
A procedure has been developed whereby a known microorganism is isolated, freeze-dried, and stored in a sterile vial for later use. In order to validate test procedures and/or laboratory results, a laboratory professional rehydrates the microorganism from its freeze-dried state by adding a sterile liquid to create a suspension containing the microorganism. A sample of the suspension is extracted and transferred to a Petri dish for culturing in order to grow colonies of the microorganism. The isolated colonies are then examined to compare their growth and response to biochemicals to known characteristics of the microorganism.
The foregoing hydration procedure requires adding the sterile freeze-dried microorganism to a sterile solution by introducing a measured quantity of hydrating fluid and agitating the solution. The addition of the hydrating solution is typically accomplished with a transfer pipette, which must be sterile to avoid contaminating the specimen. In some cases, the pipette is used to mix the solution. In others the solution may be capped in a vial and mixed to ensure complete rehydration. Care must be taken that the cap (if the original storage container is used) or the new container (if mixed separately from the original storage container) is also sterile to avoid contamination during mixing. Then, a new pipette or inoculation loop is used to extract a quantity of the solution containing the rehydrated microorganism to a nutrient-enriched medium such as agar, so that the microorganism can be cultured under controlled conditions.
A crucial step in the culturing process is the inoculation of the agar with the specimen in a manner so as to create isolated colonies so a microbiologist can observe the microorganism's morphology. Using a technique referred to a “streaking,” an inoculation device having an inoculating end, such as a loop, is typically used to spread the specimen across the surface of the agar. Typically, the Petri dish is divided into four quadrants and the microorganism suspension is placed in the first quadrant and streaked side to side. The procedure is repeated for quadrants two, three and four, with each successive quadrant reflecting diminished concentrations of the solution, to yield isolated colonies of microorganism after culturing.
The use of an inoculation loop facilitates the creation of individual colonies, which are otherwise difficult to achieve without a specialized inoculating wand. This allows the microbiologist or laboratory technician to view the morphology of the microorganism to ensure purity of the culture. The incubation period, depending on the rate of growth of the microorganism, can typically be 24 hours or longer. If the inoculation has been performed correctly and without contamination, individual colonies of microorganism may be identified, studied and compared to known results.
The foregoing prior art process is rife with opportunities for contamination that can foil the testing process and lead to false results. Contamination opportunities exist when the specimen is first exposed to airborne contaminants during the rehydration step, or to contaminated transfer pipettes or to mixing containers. Contaminated rehydrating fluid also poses an opportunity for contamination of the culture. Next, mixing in a vial introduces the potential for contamination, as the solution contacts new surfaces when the solution is shaken, stirred, or otherwise mixed. The transfer of the rehydrated specimen to a culture dish with a transfer pipette presents yet another opportunity for contaminating the specimen. Finally, the streaking of the specimen in the dish with an inoculating loop or other implement presents yet another opportunity for contamination.
The use of plastic inoculation loops and plastic transfer pipettes represents an advance over metal counterparts in decreased manufacturing costs at the expense of new sterilization problems. Heat sterilization over an open flame was used to sterilize the metal inoculation loops and glass pipettes, but this form of sterilization is unavailable when using plastic counterparts for obvious reasons. Therefore, inoculation loops and transfer pipettes must be sterilized by other means such as irradiation, electron beam, or autoclaving before packaging. However, contamination is still a constant threat because the slightest contact with any non-sterile surface, even removing the inoculating loop or transfer pipette from its packaging, can contaminate the specimen. Because the incubation period can be a day or more, the time before it may be discovered that contamination has occurred leads to inefficiency, undue delay, and frustration of the microbiologist or laboratory technician if the entire procedure must be repeated.
In addition to the constant threat of contamination, the inconvenience of stocking each separate implement used in the process is evident. Each testing requires a separate storage container, a separate sterile mixing container, a sterile transfer pipette or other sterile transfer device, and a sterile inoculation loop or other inoculation device for streaking the specimen. There is therefore a need in the art for a convenient, all-in-one storage, hydration, transfer, and streaking device that minimizes the risk of contamination in the various stages of the bacterial growth testing.